Beta-cell replacement therapy via islet transplantation remains a promising technology for the reversal of type 1 diabetes. A significant barrier to the clinical utilization of beta cell transplants has been the lack of a host-derived blood supply to maintain the viability and thus the function of transplanted cells. We have developed a new cell-based therapy for the generation of pre-vascularized tissue engineered constructs. We have also developed a new generation of biomaterials that support extensive neovascularization. The combined cell and material construct to be evaluated is termed a Prevascularized Immuno-Isolation Device or PVID. We propose to use these materials in the development of a new beta-cell immuno-isolation device to prolong beta cell viability and function. These constructs represent a pre-formed microcirculation that can be constructed from a patient's own fat-derived microvascular endothelial cells, avoiding the use of immuno- suppressive drugs. Specific aim 1 will evaluate the maturation of the microcirculation within a prevascularized construct following implantation in an animal model. Specific aim 2 will evaluate novel porous biomaterials and material surface modification to support the neovascularization of the porous material to assure perfusion of encapsulated islets. The biomaterial developed is a two component hybrid system that also provides immunoisolation for the encapsulated islets. Specific aim 3 will evaluate the viability and function of islets encapsulated in the prevascularized immunoisolation devices in an animal model of diabetes.